Optical fusing system

ABSTRACT

Claim 1. In an active optical fuze for detonating a missile warhead at a prescribed distance in front of a target, the combination comprising: A. AN OPTICAL TRANSMITTER MOUNTED ON ONE END OF THE AIRFOIL OF THE MISSILE FOR TRANSMITTING A LIGHT BEAM IN THE FORWARD DIRECTION OF THE MISSILE; B. AN OPTICAL RECEIVER MOUNTED ON THE OTHER END OF THE AIRFOIL OF THE MISSILE FOR RECEIVING THE REFLECTED LIGHT BEAM TRANSMITTED BY SAID OPTICAL TRANSMITTER; AND C. CIRCUIT MEANS COUPLED TO SAID TRANSMITTER AND TO SAID RECEIVER FOR CORRELATING THE RECEIVED LIGHT BEAM WITH THE TRANSMITTED LIGHT BEAM AND PRODUCING A FIRING SIGNAL WHEN SAID LIGHT BEAMS ARE OF A PREDETERMINED TIME COINCIDENCE.

United States Patent [72] Inventor Frederick C. Alpers Riverside, Calif. [21 1 Appl. No. 384,036 [22] Filed July 14, 1964 [45] Patented Jan. 12, 1971 [73] Assignee the United States of America as represented by the Secretary of the Navy [54] OPTICAL FUSING SYSTEM 4 Claims, 2 Drawing Figs.

[52] U.S. Cl l02/70.2 [51] Int. Cl F42c 13/02, F42c 11/06, F420 13/00 [501 Field ofSearch 102/7021; 343/7PF; 250/83.31R

[56] References Cited UNITED STATES PATENTS 2,137,598 11/1938 Vos 102/70.2P 3,125,025 3/1964 Johnson 102/70.2P 3,129,424 4/1964 Rabinow 102/70.2XP

Primary Examiner-Samuel Feinberg Assistant Examiner-Thomas H. Webb Attorneys-Q. Baxter Warner, .l. M. St. Amand and T. M.

Phillips CLAIM: 'Claim 1. In an active optical fuze for detonating a missile warhead at a prescribed distance in front of a target, the combination comprising:

a. an optical transmitter mounted on one end of the airfoil of the missile for transmitting a light beam in the forward direction of the missile;

b. an optical receiver mounted on the other end of the air-- PATENIEU JAN 1 2 I97:

MISSILE LONGITUDINAL {AXIS PULSE GENERATOR PULSE COINCIDENCE OUTPUT AMPLIFIER DETECTOR CIRCUIT FREDERICK C. ALPERS INVENTOR.

ATTORNEYS OPTICAL FUSING SYSTEM The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to an optical fuzing system and more particularly to an optical fuzing system for detonating a missile warhead at a prescribed distance in front of a target. The'invention is particularly suited to use with a shaped charged warhead for destroying armored surface targets. This type of warhead is highly effective provided that detonation is initiated approximately 5 feet in front of the target in order to allow a metal lining on the front surface of the warhead to be reformed by the explosion into a hypervelocity jet of metal that strikes a small area of the target surface with great force.

The invention involves a simple light source and optical transmitter that is mounted on one airfoil of the missile, and

an optical receiver mounted on an opposite airfoil. Both the light transmitter and receiver are collimated so that the transmitted light beam intersects the receiver beam pattern in the area ahead of the missile where the jet from the warhead will pass. In order to accommodate missile speed and any inherent firing delays, the point at which the center of these beams intersects may be somewhat forward of the desired position of the target surface at the instant of detonation of the warhead. The desired result is to initiate detonation based on the fact that at least a portion of a partially reflective surface has appeared within the intersection region of the beams. The beams have finite widths to avoid difficulties in establishing and maintaining alignment. With the shaped charge warhead there is no advantage in having the two beams wide enough to achieve overlap on a target even if it lies off the warhead axis; in this case the jet with the necessary energy to pierce modern armor would miss the target anyway since the missile cannot turn significantly in the short distance. If the missile guidance is somewhat imperfect and the missile scores a near miss, reflection of the beam from the ground or another object within the beam intersection region will lead to fuzing action that results in an above ground burst.

An object of the invention is to provide an active optical fuze for detonating a missile warhead at a prescribed distance in front of a target.

Another object of the invention is to provide an active optical fuze for detonating a missile warhead at a predetermined distance in front of a ground target.

Still another object of the invention is to provide a fuzing system which will fuze on small ground targets, such as small fortifications, tanks and armored vehicles.

Other objects and many of the attendant advantages of this invention will become readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a diagram showing the reflecting target; and

FIG. 2 is a block diagram of the system'for producing the fuze firing pulse.

Referring now to the drawings, there isshown in FIG. 1 a light source mounted on one airfoil .tip of a missile l1, and a receiver 18 located on the opposite airfoil tip from the location of transmitter 10. Light source 10 and receiver 18 are adjusted in angular orientation so that the intersection between the transmitted light beam 12 and the receiver beam pattern 16 will lie along the missile longitudinal axis at the desired fuzing distance from the missile II. The light from light source 10 is received in receiver 18 whenever the target 14 or another reflecting object comes within the region'where the transmitted light beam 12 and the receiver beam pattern 16 intersect. I

Referring now to FIG. 2 the light-source 10 is shown as a semiconductor laser 20 which may be a gallium arsenide diode that emits light at a specific infrared frequency whenever pulsed with an electrical signal from pulse generator 22. The pulse rate should be moderately high so that there are six or beam intersection and a more pulses for every foot of travel of the missile. The pulse rate may be made random to give increased countermeasures performance. Pulse widths from a small fraction of a microsecond to several microseconds can be used. The highly monochromatic light emitted by laser 20 when pulsed is formed into a beam by means of a simple reflector 24 and lens combination 26. Other light sources may be used, as for example an incandescent lamp whose beam is chopped by a shutter.

Receiver 18 consists of a simple lens 28, a spectral filter 30. a photocell 32, a pulse amplifier 34, a coincidence detector 36 and an output or firing pulse-forming circuit 38. Spectral filter 30 is transparent only in a spectral region that includes the laser wavelength. This selectivity greatly reduces extraneous signals from entering receiver 18. Photocell 32 may be of a silicon or lead sulfide type and produces output pulses corresponding to the pulses of light received. The pulses from photocell 32 are amplified in amplifier 34 which may be one or more stages of transistor or other type amplification designed to increase the energy level of its input. Coincidence detector 36, which may be an AND circuit, has an input couof amplifier 34. Detector 36 may comprise several diodes. a

gated triode, or other known circuits which give an output only when pulses are present simultaneously at each of the two inputs. The two input signals supplied to detector 36 are the pulsing signal from transmitter 10 and the output from amplifier 34 respectively, and an output will occur from detector 36 only when a signal from amplifier 36 is correlated with the timing of the pulses from transmitter 10. If very short 0.01 p. sec.) pulses are used in the system, a short delay element may be included between pulse generator 22 and detector 36 to make the electrical delay from airfoil tip to airfoil tip equal to the delay from transmitter I0 to target 14 to receiver 18 brought about by the velocity of light. In the preferred form. output circuit 38 may consist of an integrating capacitor followed by a low-impedance device such as an emitter follower or thyratron. An output is provided at the tenninal as indicated for output circuit 38 only after several coincidences have occurred in succession by the proper choice of an integrating capacitor and proper biasing of the follower or thyratron.

An alternate form of the optical receiver I8 could use a tuned amplifier and a common AC to'DC detector in place of pulse amplifier 34 and coincidence detector 36. The amplifier of the alternate form would be tuned to the transmitter pulse rate, which, to avoid undue delays in detection, would be higher than the pulse rate used in the preferred form.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

lclaim:

1. In an active optical fuze for detonating a missile warhead at a prescribed distance in front of a target, the combination comprising:

a. an optical transmitter mounted on one end of the airfoil of the missile for transmitting a light beam in the forward direction of the missile;

b. an optical receiver mount'ed'on the other end of the air- 2. In an active optical fuze for detonating a missile warhead at a predetermined distance in front of a ground target, the combination comprising:

a. an optical transmitter mounted on one end ofthe'airfoil of a missile for transmitting a light beam in th'eforward directionof the missile and intersecting withthe longitudinal axis of the missile at the prescribed detonation distance from the missile and the targetto be destroyed;

b. an optical receiver mounted on the other end of the airfoil of the missile for receiving the reflected light beam transmitted by said optical transmitter; and

c. circuit means coupled to said transmitter and to said receiver for correlating the received light beam with the transmitted light beam and producing a firing signal when said light beams are of a predetermined tim e coincidence.

3. The apparatus of claim 2 wherein said transmitter includes a pulsed laser light source.

4. In an active optical fuze for detonating a missile warhead at a predetermined distance in front of a ground target, the combination comprising:

a. an optical transmitter mounted on one end of the airfoil of a missile for transmitting a light beam in the forward direction of the missile and intersecting with the longitudinal axis of the missile at the prescribed detonation distance from the missile and the target to be destroyed;

b. an optical receiver mounted on the other end of the airfoil of the missile having light filter means for permitting only light of the same frequency of the transmitted light beam to enter; and

c. circuit means coupled to said transmitter and to said receiver for correlating the received light beam and producing a firing signal when said light beams are of a predetermined time coincidence. 

1. In an active optical fuze for detonating a missile warhead at a prescribed distance in front of a target, the combination comprising: a. an optical transmitter mounted on one end of the airfoil of the missile for transmitting a light beam in the forward direction of the missile; b. an optical receiver mounted on the other end of the airfoil of the missile for receiving the reflected light beam transmitted by said optical transmitter; and c. circuit means coupled to said transmitter and to said receiver for correlating the received light beam with the transmitted light beam and producing a firing signal when said light beams are of a predetermined time coincidence.
 2. In an active optical fuze for detonating a missile warhead at a predetermined distance in front of a ground target, the combination comprising: a. an optical transmitter mounted on one end of the airfoil of a missile for transmitting a light beam in the forward direction of the missile and intersecting with the longitudinal axis of the missile at the prescribed detonation distance from the missile and the target to be destroyed; b. an optical receiver mounted on the other end of the airfoil of the missile for receiving the reflected light beam transmitted by said optical transmitter; and c. circuit means coupled to said transmitter and to said receiver for correlating the received light beam with the transmitted light beam and producing a firing signal when said light beams are of a predetermined tim e coincidence.
 3. The apparatus of claim 2 wherein said transmitter includes a pulsed laser light source.
 4. In an active optical fuze for detonating a missile warhead at a predetermined distance in front of a ground target, the combination comprising: a. an optical transmitter mounted on one end of the airfoil of a missile for transmitting a light beam in the forward direction of the missile and intersecting with the longitudinal axis of the missile at the prescribed detonation distance from the missile and the target to be destroyed; b. an optical receiver mounted on the other end of the airfoil of the missile having light filter means for permitting only light of the same frequency of the transmitted light beam to enter; and c. circuit means coupled to said transmitter and to said receiver for correlating the received light beam and producing a firing signal when said light beams are of a predetermined time coincidence. 